1. Field of the Invention
The present invention relates to an organic anti-reflective film composition suitable for use in submicrolithography. More particularly, the present invention relates to an organic anti-reflective film composition which contains a chromophore with high absorbance at the wavelengths useful for submicrolithography, thereby allowing stable formation of ultrafine patterns suitable for use in the high integration of semiconductor devices. Also, the present invention is directed to a method for forming ultrafine patterns using such an organic anti-reflective film composition.
2. Description of the Prior Art
In a submicrolithographic process, there inevitably occurs standing waves and reflective notching of the waves due to the optical properties of lower layers coated on the wafer, due to changes in the thickness of the photoresist film applied thereon, and due to the CD (critical dimension) alteration caused by diffracted and reflected light from the lower layers. As a solution to these problems, it has been proposed to introduce into the lower part of the photoresist film an anti-reflective layer made of a material which is highly absorptive of the light whose wavelength ranges are used in the submicrolithography process.
In the absence of such an anti-reflective layer, the light, when being irradiated on the photoresist film from a UV light source, penetrates into the photoresist film and is reflected back or scattered from its lower layer or the surface of the semiconductor chip. The anti-reflective layer can be introduced to prevent the reflection or scattering of light, thereby having a direct influence on the submicrolithography process of photoresist films.
The anti-reflective film can be inorganic or organic material and is generally divided into two types depending on its mechanism: an absorptive anti-reflective film or an interferential anti-reflective film.
For the microlithography using i-line (365 nm) as a light source, inorganic anti-reflective films are usually used. Of these, absorptive anti-reflective layers are largely made from TiN or amorphous carbon (amorphous-C) while interferential anti-reflective layers are mostly based on SiON. These SiON-based anti-reflective films are also used for the formation of ultrafine patterns for which KrF (248 nm) is utilized as a light source.
As for an ArF light source, which is much shorter in wavelength than the above-mentioned two light sources, a suitable anti-reflective films pertinent to submicrolithography has not yet been developed. Currently, there is an extensive research directed to the development of organic anti-reflective materials which are suitable for use in an ArF light submicrolithography process.
Following are desired characteristics for organic anti-reflective materials:
First, peeling of the photoresist layer due to dissolution of the organic anti-reflective material in a solvent should not take place when conducting a lithographic process. In this regard, organic anti-reflective materials should be designed so that their cured films have a crosslinked structure without producing by-products.
Second, there should be no migration of chemical materials, such as acids or amines, to and from the anti-reflective layers. If acids migrate from the anti-reflective layer into an unexposed area of a positive photoresist film, the photosensitive patterns are undercut while the egress of bases, such as amines, causes a footing phenomena.
Third, faster etch rates should be realized in the anti-reflective layer than in the upper photosensitive film, allowing an etching process to be conducted smoothly with the photosensitive film serving as a mask.
Finally, organic anti-reflective layers should be as thin as possible while having a superior ability to prevent light reflection.
The present invention provides an anti-reflective resin which meets the above requirements. In particular, it has been found that anti-reflective resins of the present invention are suitable for use in ultrafine pattern formation using ArF light source.
Another embodiment of the present invention provides a method for preparing an organic compound which reduces or prevents the diffusion and reflection of light in a submicrolithography process.
Yet another embodiment of the present invention provides an anti-reflective composition containing such an organic diffusion/reflection-preventive compound and a method for preparing the same.
Still another embodiment of the present invention provides a method for forming a pattern with a greatly reduced standing wave effect on a semiconductor device using an ArF laser submicrolithography process.
Still yet another embodiment of the present invention provides a semiconductor device on which a pattern is formed from such an anti-reflective composition by submicrolithography.